1. Field of the Invention
This invention relates to a container of coolant used in a stepper, and more particularly to a container of coolant utilizing a screw cap to air-tightly close a coolant inlet of the container of coolant.
2. Description of Related Art
The products of integrated circuits (ICs) are existing everywhere in our daily life but the fabricating procedure of the products of ICs is very complicated. Generally, it needs a few hundreds of different steps and takes one or two months to compete a production. The industry of ICs has four main categories including the design of ICs, the fabrication of a wafer, the test of a wafer and the package of a wafer. Therefore, the industry of ICs not only needs a high technology of science but also needs a great amount of funds to support and keep the continuous developing. This causes a high risk on the industry of ICs.
From the point of view of the fabrication of a wafer, it further includes oxidation, diffusion, deposition, pattern, etching and so on. In the fabricating procedure of photolithography, so far, a stepper is usually applied for the fabrication of a wafer.
While a stepper is under the operation for fabricating the wafer, it is very important to keep the temperature and the humidity of the stepper in a certain acceptable range. If the temperature and the humidity were out of the range, the stepper would produce some errors in the fabricating procedure or even could be breakdown. Therefore, the conventional stepper has made use of coolant for maintaining the temperature and the humidity.
Freon (CCl.sub.2 F.sub.2), a coolant, is odorless, nonpoisonous, nonflammable and noncorrosive so that freon is a good candidate of coolant and, thus, is widely used in the stepper, which has a container of coolant to avoid the problems due to the temperature and humidity having been out of acceptable range.
FIG. 1 illustrates the top view of a conventional container of coolant. FIG. 2 illustrates the front view of a conventional container of coolant. FIG. 3 illustrates the perspective view of an exploded conventional container of coolant.
Referring to FIGS. 1-3, a conventional container of coolant 9 used in a NIKON.TM. stepper 8 with being mounted on machines of types I8, I9 and I10. The structure of the container of coolant 9 includes a storing container 10, a metal plate 14 and a washer 12. The storing container 10 is made of stainless steel and is used for storing a coolant. The storing container 10, with a top and a bottom, has a coolant inlet 11 on the top. The coolant inlet 11 is closed by tightly screwing the six screws 16. The screws 16 distributed evenly on the rim of the metal plate 14 are through the metal plate 14 and the washer 12 to be screwed tightly on the storing container 10. The metal plate 14 has an up-lifter 18 around the center to allow the metal plate 14 to be lifted up. The storing container 10 further has four mounting holes 20 on the bottom for allowing the storing container 10 to be mounted on the stepper 8. In addition, the storing container 10 has a circulative output duct 22 and a circulative input duct 24 for connection with a coolant compressor 100 as shown FIG. 2. The coolant compressor 100 processes the coolant and drives the coolant in circulation through the circulative ducts 22, 24.
For the conventional container of coolant 9, as described above, the coolant inlet 11 is closed by using six screws 16 to tighter the metal plate 14 and the washer 12. If the exerted tightness on each of the screws 16 is not uniform, coolant can leak out from a gap on the periphery of each of the screws 16. Moreover, the leakage of coolant can possibly happen on the up-lifter I8 even though the up-lifter 18 is convenient for lifting the metal plate. If the leakage happens, the insufficient coolant can easily induce the problems on the stepper 8 and cause the errors.
In the description above, the conventional container of coolant 9 has some drawbacks as follows:
1. The method to close the coolant inlet 11 is using six crews 16 through the metal plate and the washer 12 to screw tightly on the storing container 10. If the exerted tightness on each of the screws 16 is not uniform, coolant can leak out from the gap on the periphery of each of the screws 16. PA0 2. The leakage of coolant can possibly happen on the up-lifter 18 even though the up-lifter 18 is convenient for lifting the metal plate.